1. Field of the Invention
The present invention relates to a radiographic image connection processing method, a radiographic image connection processing apparatus, a computer program for executing the radiographic image connection processing method, and a computer-readable recording medium storing the computer program for executing the radiographic image connection processing method. In particular, the present invention relates to a technique which is suitable for generating a whole image based on plural partial radiographic images generated from a common subject portion.
2. Related Background Art
Conventionally, a so-called radiographic image diagnosis which obtains an image of a patient by using electromagnetic radiation (X-rays) and thus obtains internal information about the patient is widely executed. Here, in conventional radiography, a film is held together with an intensifying screen in a cassette, a patient is photographed using radiation rays, and the photographed film is developed, whereby a radiographic image of the patient is obtained.
The size of the film to be used at that time is standardized, and the maximum film that is generally and widely used is a so-called half-size film, having the size 14 inches×17 inches.
In a case where so-called lower limb whole-length photographing or whole spine (or backbone) photographing, which aims to measure a bone, is performed, the half-size film of 14 inches×17 inches is too small in size to be used. Thus, in that case, there is used a method in which a so-called long cassette capable of holding a long film is used to photograph a whole-length lower limb or a whole spine and thus obtain the image thereof on the long film. However, even in that case, another method may be adopted because it is hard for an operator to deal with the long film when developing it. In this alternative method, plural half-size films (each 14 inches×17 inches) are held in the long cassette so that the successive films partially overlap each other, and the image obtained by photographing the whole-length lower limb or the whole spine is formed on these films. Further, in this method, the films on which the photographed image has been formed are developed one by one, and then the developed images are appropriately connected with each other using adhesive tape or the like, to obtain the whole image.
On one hand, in recent years, an apparatus which can directly photograph a subject and thus obtain a radiographic image thereof as a digital image has been developed. Japanese Patent Application Laid-Opens Nos. S55-012429 and S63-189853 and the like disclose, e.g., a method in which a photostimulable phosphor detector is used as an apparatus for detecting an amount of radiation irradiated on the subject and then forming as an electrical signal the radiographic image in correspondence with the detected amount of the radiation.
In the apparatus like this, photostimulable phosphor is applied or evaporated on and then fixed to a sheet-like substrate to form the photostimulable phosphor detector, and the radiation transmitted through the subject is irradiated on the formed detector, whereby the irradiated radiation is absorbed by the photostimulable phosphor. Then, the photostimulable phosphor is excited by light or heat energy, the radiation energy stored in the photostimulable phosphor as the result of the above absorption is emitted as fluorescence, and the emitted fluorescence is photoelectrically converted, thereby obtaining the electrical image signal.
In addition, Japanese Patent Application Laid-Open H03-287248 proposes a method of performing, e.g., whole spine photographing by using such an apparatus as above. In this method, more specifically, a long cumulative phosphor sheet which has a recording area corresponding to the length of the whole spine of a subject is used to perform the photographing.
Moreover, Japanese Patent Application Laid-Open No. H11-244269 proposes a method in which plural cassettes respectively holding photostimulable phosphor detectors are arranged partially overlapping each other, the cassettes are held in this arrangement in a special cassette holder, and the subject is photographed.
Japanese Patent Application Laid-Open No. H03-287249 proposes a method in which plural photostimulable phosphor detectors are arranged partially overlapping each other, a subject is photographed to obtain plural partial radiographic images, and then the partial radiographic data corresponding to these images are synthesized to generate a whole image.
On one hand, in recent years, an apparatus which can photograph a subject by using a semiconductor sensor and obtain a radiographic image thereof as a digital image is developed. More specifically, in this type of apparatus, which uses the semiconductor sensor, generally, phosphor is applied or adhered to the semiconductor sensor in advance. Thus, incident radiation is first converted into light by the applied or adhered phosphor, the converted light is detected by the semiconductor sensor, and the detected light is then photoelectrically converted into an electrical signal.
In the apparatus of this type, because the area photographable by the semiconductor sensor is limited or restricted, it is impossible to photograph the whole spine of a subject with one exposure. For this reason, the subject is photographed plural times to obtain plural partial radiographic images, the obtained plural images are displayed, and whole-image data, representing a single whole image, is then generated based on plural sets of partial radiographic image data corresponding to the displayed plural images.
Japanese Patent Application Laid-Open No. 2000-342567 proposes a method of generating whole-image data from plural partial radiographic image data respectively obtained by photographing a subject plural times. According to this method, generally, a user interactively generates the whole image data. More specifically, in a synthesis image generation step to be performed in this method, the radiographic image of the subject (target) is first displayed, the partial radiographic images to be synthesized are appropriately selected from the displayed image, the connection positions at which the successive partial radiographic images should be connected with others are designated respectively on the selected partial radiographic images, and the partial radiographic images are actually connected and synthesized on the basis of the designated connection positions, thereby generating a whole image. As described above, various examples for mutually synthesizing or connecting the plural partial radiographic images are proposed, but none of these examples mention a problem which may occur during in measuring the radiographic image.
In a case where plural radiographic images are connected as above, when position adjustment of the radiographic images and measurement of the radiographic images are simultaneously performed, there is a fear that the position adjustment of the images may shift immediately after the measurement of the images, and, in such a case, the connected and synthesized image is different from the measured result.
Moreover, in a case where a mark used for the position measurement and/or the measured result obtained by the position measurement are displayed on the radiographic images, there is a fear that the mark and/or the result remaining on the display may interfere with the position adjustment of the radiographic images and/or the measurement of the radiographic images, which are the intended purpose.
Furthermore, in a case where a distance extending across the successive radiographic images is measured and then an enlargement ratio of one of these images is changed, there is a fear that the accuracy of the measured result may suffer.